1. Field of the Invention
The invention relates to a method for processing video data and apparatus thereof, and more specifically, to a method for examining image blocks corresponding to a pure film mode or a mix film mode.
2. Description of the Prior Art
The traditional interlaced scanning shows an image frame of a film by interlacing two fields contained in that image frame. Because of physiologic photogene, observers won't feel odd regarding the image shown. The two fields are the odd field which is composed of odd scanning lines, and the even field which is composed of even scanning lines.
A new technique called progressive scanning, which is also referred as non-interlaced scanning, combines the two fields of one frame and then scans the frame progressively with doubled horizontal scanning frequency.
Nowadays, the film modes are determined by the relationship of each field in video data (i.e. 2:2 Pull Down or 3:2 Pull down). The de-interlacing will be performed after film mode is determined. However, when a movie is played, marquee captions, fixed text or trademarks sometimes show up on screen due to advertisements or special effects. In other words, a lot of video data is not in pure film mode, indicating that the film mode and non-film mode exist in one movie simultaneously. This kind of video data belongs to a mix film mode. Using the traditional detecting techniques to detect the mix mode movie will lead to two results. The first result is that the film mode content is not detected, so it is not processed through the film mode protocol. As a result, the quality of the film mode content is deteriorated. The second result is that portions of non-film mode is referred wrongly as film mode, and is therefore processed through a film mode mechanism. Accordingly, sawtooth or blur marquee caption is created.